Solubilized nitrocellulose



Patented July 28, 1931 UNITED STATES PATENT OFFICE CARLETON ELLIS, OF MONTCLAIR, .,NEW JERSEY, ASSIGNOR TO ELLIS-FOSTER COM- PANY, A CORPORATION OF NEW JERSEY SOLUBILIZED NITRDCELLULOSE NoDraWing. Application filed December 24, 1923, Serial No. 682,553. Renewed October 1, 1929.

This invention relates to a process of male mg a nitrocellulose product of low viscosity and relates particularly to a method of heat 1 treatment of nitrocellulose, pyroxylin and similar nitro esters to yield more soluble or less viscous solutions adapted for use in making lacquers, paints, cements and for various other purposes.

In one form the invention is concerned with the reduction of viscosity of celluloid or compositions containing nitrocellulose and camphor, while in another instance nitrocotton or other nitrocellulose is treated. With reference to the celluloid form of the invention, moving picture film is especially adapted for use in carrying out the present manner of treatment. A large amount of moving picture film after circulation is returned to the makers and the emulsion is stripped from the surface of the film. This stripped film is used as a cheap source of nitrocellulose. Solutions made from such material have however a relatively high viscosity which restricts their use. With only a few ounces of the nitrocellulose per gallon the solution becomes too thick to be used for many purposes.

en moving picture film is subjected to heat as for example in the manner indicated in Serial 522,915, filed December 16, 1921, by Ellis and Weber process and apparatus for treating films, where a procedure is indicated involving passing the film through boiling water, hot salt solutions, hot acid solutions and the like some shrinkage occurs which renders the film unsuitable for re-sensitizing but when used for making lacquers, artificial leather coatings, automobile paints and the like a product of improved solubility or viscosity is obtained.

After the film has been stripped in this or in any other suitable manner it may be subjected, in accordance with the present invention to brief but intensive heating in order to reduce the viscosity to a still lower point.

Preferably the film is passed continuously through a heating zone wherein it is exposed for a period of say from one to five minutes to a temperature approximating the point at which vigorous decomposition occurs. Thus when the film is exposed to a tempera ture abov 1.31)" (l. and preferably at 160 C. for a br f time interval it becomes enormously reduced in viscosity. If the heating is carried out at 170 C. for example, or at some ten'iporature approximating the. point of vigorous decomposition of the nitrocellulose the transparent film will turn White and opaque and becomcfilled with large blisters containing nitrous gases. The film in this condition presents a puffed appearance and the temperature of this occurrence may be designated as the pufiing point. A temperature a few degrees below the putting point is desirable.

It should be stated that thcpresent invention contemplates the avoidance of the dangers from fire and explosion involved in heating large masses of nitroecllulose at lower temperatures for a long period of time to reduce the viscosity. Thus for example by baking moving picture film at a temperature of 100 C. for several hours a very substantial decrease in viscosity will occur. However the danger involved in heating a large batch of moving picture film for this period of time is considerable.

The intensive heating referred to above accomplishes in minutes a change which at 100 C. may require a like number of hours.

This permits of passing the celluloid ma-- terial or other pyroxylin substance continuously through a heating zone and since only a small portion of the material need be ex: posed at any one instant to this high temperature heat and furthermore since it is possible to have safety devices to protect the mass of material feeding into the heating Zone and similar devices for the hot material leaving the heating zone. there is little danger of great damage and lo s through violent explosions.

f a fire occurs in the heating zone it will simply cause the combustion of the small amount of mat rial therein.

in the following description I shall particularly describe processes carried out in a continuous manner but I do not wish thereby to exclude the possibility of high temdrawn from the heating Zone the film was temperature of about 170 C. for a period or into water or handled in aii found'to be substantially unchanged in ap pearance although slightly less tough and elastic than the unheated film.

This film dissolved readily in solvents: such as acetone and formed solutions of very low viscosity. For example 10 grams'of the film dissolved in 100 c. c. of acetone in certain viscosity tests passed through the viscosi-' meter in 45 seconds. The term 15 seconds as used at this pointis a comparative term,

and when rated on the usual lacquer vis cosity determination basis now employed in the art may be considered to represent a viscosity on the latter basis of less than onehalf second. A solution of like strength of the unheated film tested for viscosity under like conditions required 24 minutes. It will thus be seen that this very brief treatment at a temperature approaching the puffing point accomplishes an enormous decrease in viscosity. Such thin solutions find a much wider range of use in making lacquers, paints and for various other purposes than is the case with the solutions made from the untreated celluloid.

In another case the film was exposed to a of between 2 and 5 minutes yielding a white puffed-up opaque product. Certain parts of'the film appear to be more sensitive than others depending possibly on slight irregularities incomposition, and the film is therefore preferably exposed to a heat which is below the puffing point of any part of the film. However a small amount ,of pufi'ed material, that is a few. local puffed places is not objectionable in many cases.

Ordinary celluloid scrap such as the cuttings and saw dust collected in the manufacture of celluloid combs and other articles may betreated by passing through a heated drum under conditions more or less similar preferably with the employment of safety devices to prevent ignition of'the raw material or the hot treated material The latter may be dischar into a col mosphere other way to promote a maximum degree of safety.

In like manner nitrocellulose in various other forms such as the nitrocotton and the like may be heat-treated. However the invention is specifically concerned with the treatment of celluloid, that is nitrocellulose incorporated with camphoror similar substance, and the preferred embodiment involves the treatment of stripped moving.

picture film preferably in a continuous or non-cumulative manner.

The heating drum or oven or whatever device is used for maintaining the heatingzone may employ an atmosphere of ordinary air or inert gas or superheated steam. The latter is preferable in view of its ease of application and tendency'to reduce fire by heating in boiling water in the manner set forth in Serial 522,915the shrinkage of the film may be used as a rough index of increased solubility and reduced viscosity. To produce material which will make highly concentrated solutions a shrinkage of for example one-fourth the width of the film is sometimes desirable.

In one case heating the film in a 5 per cent caustic soda solution. for a period of 5 minutes reduced the viscosity from 24 minutes as noted above to approximately 10 minutes. Such material may be further treated by exposure to dry heat at a temperature near the putting point to solubilize the nitrocellulose.

The material made in accordance with the present process may be dissolved in a suitable solvent such as a mixture of acetone and ethyl acetate and after careful filtration may be employed in the manufacture of fibers and the like.

Solutions may be made from this highly solubilized nitrocellulose material with great ease, employing alcohol, acetone, ethyl acetate and the like and also mixtures of such solvents with non-solvents such as benzol. and petroleum spirits. High boiling solvents may be introduced such as amyl'iacetate, fusel oil, butyl alcohol, diacetone alcohol and. the like. i

Softening agents such as diethyl phthalate, benzyl alcohol and benzyl acetate, camphor and camphor substitutes also may be added. Stabilizers such as urea and various other compounds may be added to the solution in case of any acidity developed by the prior heating to temperatures near the puffing point.

These solutions may be used in coating leather, manufacture of lacquers, and particularly in the preparation ,of automobile paints which require pronounced resistance to weather} conditions. The solution of the solubilized nitrocellulose in volatile solnot which I believe to be new.

vents with some high boiling solvent or water-eliminant may be incorporated with gums such as damar or copal gums, shellac and the like. i

Synthetic resins may also be incorporated to advantage as for example resins made from glycerol and phthalic acid, or from ordinary rosin, glycerol and phthalic acid. Such resins mix or blend with cellulose admntagcously and can be made of various degrees of hardness or softness so that they are more flexible for the purpose of manufacturing nitrocellulose paints for automobile purposes. r

A suitable pigment which may be ground in castor oil is added. Such pigments include the various mineral or earth colors ochre, umber and the like and also various lake colors.

Heretofore a great difficulty has been ex perienced' from making solutions of nitrocellulose and. resins with pigments which can be applied readily by spraying or by brushing. The present method of solubilizing celluloid to this high degree makes possible a coating composition having the tough elastic qualities and hardness of nitrocellulose not necessarily however the jelly-like properties characteristic of most concentrated nitrocellulose preparations. The invention therefore greatly broadens the field of coatings for automobiles and furniture and so forth.

Finally it may be added that the material treated in accordance with my invention, that is momentary or very brief exposure to relatively high temperature yields a pro'd- The reactions which take place under such intensive heating within the controlled limits specified afford a solubilized material rather than one of simply reduced viscosity. The product of the present invention includes but is not limited to a solubilized product, capable even when in concentrated solution of being substantially devoid of the colloidal and gelatinous properties characteristic of nitrocellulose constitutes a phase of the invention expressed by certain of the appended claims.

Nitrocellulose treated as set forth herein is so reduced in viscosity that it appears to all intents and purposes more soluble from the practical standpoint.

What'I claim is 1. The process of making solubilized celluloid which comprises exposing stripped nitrocellulose film for a short time to an intensive heat at or near the pufling point.

2. The process of making solubilized celluloid which comprises passing stripped nitrocellulose film continuously through a heated zone at a temperature above 150 C. but not exceeding the pulling point of said nitrocellulose, the exposure to heat being for a period not exceeding approximately five minutes.

3. The process of treating celluloid which comprises passing celluloid material continuously through a zone maintained at a temperature'of about 160 (3., the period of exposure not exceeding two to five minutes.

4. The process of making solubilized material for a short time to an intensive heat at or near the pufiing point in an atmosphere of an inert gas.

6. The process of making solubilized celluloid which comprises exposing celluloid material for a short time to an intensive heat at or near the pulling point in the presence of super-heated steam.

7 The process of treating celluloid which comprises subjecting celluloid material to treatment with a solution to reduce its viscosity, and then exposing said treated material to a dry heat at a temperature near but not above the pulling point to solubilize said material.

8. The process of treating celluloid which comprises treating celluloid material with a hot-aqueous liquor to improve its solubility, and then subjectingthe treated material to intensive heating at a temperature not above the pufiing point to further reduce the viscosity of the product.

9. As a new product celluloid solubilized by brief exposure to a temperature of 160 C.

10. As a new product celluloid solubilized by exposure for a period not exceeding five minutes to a temperature near the putting point.

11. As a new product celluloid solubilized by intensive heat at a temperature near the putting point, said treated material having a viscosity of less than one-half second.

12. The process of treating nitrocellulose to reduce its viscosity which comprises subjecting nitrocellulose in a continuous manner to intensive heating at a temperature not above the puffing point.

13. The process of treating nitrocotton to reduce its viscosity which comprises passing such nitrocotton in a continuous manner in the presence of steam through a heating zone maintained at a temperature at which nitrocotton falls rapidly in viscosity but below the pufling point.

14. The process of treating nitrocotton to reduce its viscosity which comprises passing such nitrocotton in a continuous manner in the presence of a non-supporter of combustion comprising steam through a heating zone maintained at a temperature at which nitrocotton falls rapidly in viscosity but below the pufling polnt.

15. As a new product, nitrocotton substantially reduced in viscosity by intensive heat at a temperature near the puffing point, said product being easily solublevin nitrocellulose solvents and forming solutions adapted for use as coating compositions.

} 16. As a new product, nitrocotton substantially reduced in viscosity by intensive heating at a temperature at which nitrocotton falls rapidly in viscosity but below the pufling point, said product being easily soluble in nitrocellulose solvents and forming solutions adapted. for use in coating compositions.

' CARLETON ELLIS.

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